I’m using PROOF to process a large chain of root files (coming from xrootd server). I saw the example of tree friends and wondered if using this concept of tree friend (without using CopyTree) there is a way to create an additional binary branch (in another TTree/TFile) that indicates some cuts were passed after some (sometimes heavy) calculations in order to save computing time next time I process the same files and without the need to copy the content of the initial TTree? If so, is there any example available on how to achieve this?